Conventional robot cleaners generally comprise a dust suction unit, which includes a suction port and a rotary brush, a suction motor which provides a vacuum source, a sensor unit which includes an obstacle sensor and a distance sensor measuring a traveling distance and location, driving rollers mounted on both sides thereof, a driving motor for driving the driving rollers, a diverting roller mounted on front and rear sides thereof, and a control unit which controls the dust suction unit, the sensor unit and the driving unit.
The dust suction unit of a conventional robot cleaner usually uses a dust bag made of paper or fabric to collect dust therein. The dust bag also serves as a filter. When using a dust bag made of plastic, a predetermined filter is often separately installed to filter air and discharge the filtered air toward the suction motor. However, when the dust bag is full or the dust receptacle is blocked, the suction force drops considerably, accordingly deteriorating cleaning performance.
Also, conventional robot cleaners generally use a rechargeable battery, which supplies limited amounts of electric power, and accordingly uses a small-size suction motor consuming relatively less power to maintain compact size of the robot cleaner. However, such a small-size suction motor has lower suction efficiency than general suction motors.
In order to overcome the limited suction efficiency of the small-size suction motor, a cyclone structure has been widely used, which is superior to the dust bag with regards to the suction efficiency and even recyclable. Exemplary robot cleaners adopting such a cyclone structure are disclosed in British Patent No. 2344778 and Korean Patent No. 333880, the subject matter of each of which is incorporated by reference.
In British Patent No. 2344778, cyclone units having a conical shape are laterally mounted. However, since this structure increases the volume of the cyclone unit, the robot cleaner is bulky and not compact. In the robot cleaner disclosed in Korean Patent No. 333880, a cyclone unit having a cylindrical form is vertically mounted into a cleaner body and is fluidly communicated through a separate suction pipe connected to a suction port. This structure also makes it hard to compactly design the robot cleaner because the dust receptacle connected to a lower part of the cyclone unit increases the height of dust collection unit.
Furthermore, the cyclone structures as disclosed in British Patent No. 2344778 and Korean Patent No. 333880 have a longer dust suction path for generating a rotating air current than the dust bag structure. The long dust suction path causes loss of energy due to friction with the rotating air current, thereby seriously deteriorating the initial suction force.
If a medium-size motor having higher suction efficiency is used, more rechargeable batteries are required to supply more electric power for driving the medium-size motor. However, this increases weight of the robot cleaner. Additionally, when adopting the cyclone structure in a robot cleaner, centroid of the robot cleaner inclines to the upper side as the height of the robot cleaner is increased. If the robot cleaner climbs an obstacle, such as a doorsill, the robot cleaner may fall down and be damaged.